Coyote Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Coyote Observatory clear sky chart from 2005-11-06 to 2024-01-15.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
28%
22584
13%
74777
8%
22540
35%
22540
15%
53648

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 10thNight
13%
760
7%
2649
2%
757
19%
757
7%
2145
January11th to 20thNight
18%
737
9%
2577
4%
737
24%
737
7%
2050
January21st to endNight
19%
792
13%
2667
6%
792
28%
792
12%
1962
February1st to 10thNight
14%
720
8%
2340
2%
720
21%
720
10%
1819
February11th to 20thNight
16%
702
13%
2275
4%
700
28%
700
12%
1676
February21st to endNight
22%
592
14%
1798
6%
592
32%
592
13%
1337
March1st to 10thNight
18%
720
14%
2124
7%
720
26%
720
14%
1590
March11th to 20thNight
20%
720
16%
1980
7%
720
30%
720
17%
1434
March21st to endNight
26%
792
20%
2087
8%
792
34%
792
19%
1484
April1st to 10thNight
21%
720
15%
1800
5%
720
26%
720
18%
1328
April11th to 20thNight
25%
711
17%
1775
6%
711
31%
711
20%
1285
April21st to endNight
27%
604
16%
1684
6%
604
35%
604
18%
1252
May1st to 10thNight
33%
360
17%
1440
14%
360
42%
360
17%
946
May11th to 20thNight
31%
354
20%
1416
14%
354
47%
354
19%
875
May21st to endNight
37%
389
14%
1551
12%
388
48%
388
23%
912
June1st to 10thNight
36%
360
9%
1440
8%
360
44%
360
15%
933
June11th to 20thNight
39%
360
13%
1440
16%
360
47%
360
20%
866
June21st to endNight
43%
360
10%
1440
11%
360
49%
360
17%
947
July1st to 10thNight
48%
350
15%
1400
18%
350
57%
350
24%
804
July11th to 20thNight
51%
348
15%
1392
20%
348
57%
348
24%
812
July21st to endNight
52%
394
15%
1486
15%
372
58%
372
24%
861
August1st to 10thNight
51%
432
15%
1496
13%
430
56%
430
23%
933
August11th to 20thNight
54%
534
18%
1598
13%
534
58%
534
31%
1010
August21st to endNight
46%
771
18%
1959
8%
771
50%
771
30%
1294
September1st to 10thNight
44%
720
16%
1800
6%
720
47%
720
31%
1199
September11th to 20thNight
51%
720
21%
1800
13%
720
54%
720
34%
1172
September21st to endNight
43%
720
20%
2047
15%
720
47%
720
26%
1363
October1st to 10thNight
34%
720
17%
2160
11%
720
42%
720
19%
1481
October11th to 20thNight
24%
720
13%
2160
7%
720
32%
720
15%
1596
October21st to endNight
22%
792
12%
2489
6%
792
31%
792
12%
1871
November1st to 10thNight
26%
740
15%
2432
10%
740
35%
740
16%
1693
November11th to 20thNight
20%
760
14%
2660
9%
760
29%
760
12%
1933
November21st to endNight
19%
760
9%
2660
5%
760
25%
760
9%
2067
December1st to 10thNight
15%
760
7%
2660
3%
760
20%
760
7%
2196
December11th to 20thNight
15%
760
11%
3246
5%
759
24%
759
7%
2477
December21st to endNight
12%
830
5%
4849
2%
817
17%
817
4%
4045

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
17%9%47%6%45%5%5%6%33%
74741
Night
17%10%47%6%35%45%6%32%
75025
TransparencyDay
51%7%11%19%10%1
74446
Night
52%7%11%19%10%1
74854
SeeingDay
22%16%30%20%9%3
13330
Night
22%14%30%24%9%1
22591

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
14%16%6%11%9%5%45%5%5%21%
1517
11th to 20thDay
18%15%6%11%8%35%44323%
1472
21st to endDay
12%14%5%11%8%5%5%5%45%24%
1688
February1st to 10thDay
14%15%5%12%9%46%5%45%22%
1620
11th to 20thDay
12%14%7%10%7%5%4445%28%
1573
21st to endDay
20%12%49%7%46%5%4424%
1456
March1st to 10thDay
16%12%5%10%7%44445%29%
1830
11th to 20thDay
15%12%5%8%8%45%445%31%
1980
21st to endDay
18%10%47%5%34445%37%
2268
April1st to 10thDay
22%12%36%5%345%46%31%
2160
11th to 20thDay
21%9%36%43444437%
2134
21st to endDay
22%10%48%6%24446%32%
2290
May1st to 10thDay
20%8%36%5%35%45%5%35%
2520
11th to 20thDay
16%9%36%6%335%5%7%38%
2478
21st to endDay
16%6%36%6%35%5%5%7%38%
2725
June1st to 10thDay
20%9%36%6%45%5%6%6%31%
2520
11th to 20thDay
15%5%36%6%45%5%6%7%39%
2520
21st to endDay
17%7%36%6%46%5%6%8%32%
2520
July1st to 10thDay
10%6%25%447%6%7%8%39%
2520
11th to 20thDay
10%6%35%6%35%6%7%9%39%
2520
21st to endDay
12%425%6%35%6%7%10%38%
2744
August1st to 10thDay
11%5%26%7%45%6%7%7%39%
2429
11th to 20thDay
12%5%27%6%46%6%5%8%39%
2303
21st to endDay
14%6%26%5%35%6%7%8%39%
2378
September1st to 10thDay
13%6%25%6%45%5%5%8%41%
2160
11th to 20thDay
13%5%25%5%35%5%48%44%
2160
21st to endDay
17%6%35%5%35%5%6%6%40%
1910
October1st to 10thDay
20%8%47%5%345%46%34%
1800
11th to 20thDay
21%10%47%5%5%5%45%7%27%
1800
21st to endDay
27%10%36%6%34445%27%
1865
November1st to 10thDay
14%10%47%436%6%5%6%35%
1643
11th to 20thDay
18%11%48%7%5%5%5%5%6%28%
1520
21st to endDay
20%13%6%9%7%5%5%446%20%
1520
December1st to 10thDay
21%18%7%11%7%45%445%15%
1520
11th to 20thDay
19%14%5%8%7%44446%25%
1906
21st to endDay
28%16%6%13%5%2332319%
2772
January1st to 10thNight
16%15%7%11%8%45%6%5%5%17%
2649
11th to 20thNight
16%16%6%11%9%35%44422%
2577
21st to endNight
11%14%6%9%8%35%5%45%29%
2667
February1st to 10thNight
13%14%6%11%8%45%5%5%6%21%
2340
11th to 20thNight
13%12%6%10%8%35%45%5%30%
2273
21st to endNight
15%11%5%8%7%445%5%6%28%
1798
March1st to 10thNight
16%13%5%8%7%45%44429%
2114
11th to 20thNight
14%12%6%8%5%34445%34%
1979
21st to endNight
16%8%47%6%3445%6%37%
2087
April1st to 10thNight
21%9%48%5%34446%34%
1800
11th to 20thNight
20%8%37%6%34446%37%
1775
21st to endNight
20%9%37%7%35%445%32%
1684
May1st to 10thNight
19%8%35%5%35%5%5%5%37%
1440
11th to 20thNight
19%7%245%34447%41%
1415
21st to endNight
12%5%25%6%35%5%6%8%45%
1550
June1st to 10thNight
16%6%36%6%45%6%6%9%34%
1440
11th to 20thNight
14%6%36%5%245%6%7%43%
1440
21st to endNight
15%7%25%6%45%5%6%8%38%
1440
July1st to 10thNight
9%6%35%5%25%5%5%8%46%
1440
11th to 20thNight
11%5%25%5%445%6%10%43%
1440
21st to endNight
9%425%5%46%5%7%9%44%
1574
August1st to 10thNight
9%6%26%6%5%45%7%9%42%
1506
11th to 20thNight
8%6%35%5%35%6%6%8%47%
1598
21st to endNight
11%6%35%5%25%5%5%8%45%
1959
September1st to 10thNight
12%6%26%5%345%47%46%
1800
11th to 20thNight
15%5%245%3435%6%49%
1800
21st to endNight
16%6%25%6%3436%6%43%
2047
October1st to 10thNight
18%8%36%5%3445%6%37%
2160
11th to 20thNight
20%10%37%6%35%45%7%30%
2160
21st to endNight
22%11%46%6%35%5%5%6%27%
2489
November1st to 10thNight
18%10%46%6%3445%6%34%
2432
11th to 20thNight
17%11%47%7%35%45%7%29%
2660
21st to endNight
20%14%5%9%6%4445%6%23%
2660
December1st to 10thNight
20%17%6%9%7%46%45%418%
2660
11th to 20thNight
20%14%6%9%6%3444426%
3288
21st to endNight
29%17%6%11%6%3333316%
4884

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
63%7%11%14%5%
1518
11th to 20thDay
67%5%7%10%10%1
1472
21st to endDay
62%5%10%13%9%1
1688
February1st to 10thDay
65%5%9%15%41
1620
11th to 20thDay
58%5%12%15%9%1
1582
21st to endDay
61%6%9%13%9%1
1456
March1st to 10thDay
57%6%10%16%10%1
1833
11th to 20thDay
55%6%10%15%11%3
1980
21st to endDay
50%5%7%18%14%6%
2268
April1st to 10thDay
54%5%7%18%12%3
2160
11th to 20thDay
49%6%7%21%15%2
2134
21st to endDay
54%5%8%14%15%4
2290
May1st to 10thDay
50%6%8%18%14%3
2520
11th to 20thDay
45%6%9%21%17%2
2482
21st to endDay
44%8%12%20%13%2
2725
June1st to 10thDay
52%8%10%18%11%1
2520
11th to 20thDay
42%9%10%23%13%3
2520
21st to endDay
48%9%12%19%11%1
2520
July1st to 10thDay
37%9%13%26%14%1
2450
11th to 20thDay
37%9%17%24%11%
2445
21st to endDay
39%10%15%26%10%
2591
August1st to 10thDay
40%10%16%23%10%
2415
11th to 20thDay
41%10%15%25%8%1
2303
21st to endDay
40%8%16%25%11%1
2378
September1st to 10thDay
40%8%14%27%11%
2160
11th to 20thDay
37%8%13%29%13%
2160
21st to endDay
44%8%13%26%9%
1910
October1st to 10thDay
50%7%11%21%10%1
1800
11th to 20thDay
56%8%14%16%6%1
1800
21st to endDay
59%7%12%15%6%1
1865
November1st to 10thDay
47%8%16%22%6%1
1643
11th to 20thDay
56%7%13%14%8%1
1520
21st to endDay
65%8%12%9%6%1
1520
December1st to 10thDay
69%7%11%8%31
1520
11th to 20thDay
61%8%13%13%5%
1906
21st to endDay
73%47%13%3
2772
January1st to 10thNight
67%7%10%12%4
2649
11th to 20thNight
66%5%9%11%7%1
2577
21st to endNight
56%6%9%17%10%1
2667
February1st to 10thNight
62%6%11%14%6%1
2340
11th to 20thNight
56%6%11%19%7%1
2275
21st to endNight
55%6%10%18%10%
1798
March1st to 10thNight
57%6%11%16%9%1
2124
11th to 20thNight
52%5%10%19%11%2
1980
21st to endNight
48%5%8%20%14%4
2087
April1st to 10thNight
51%6%9%18%14%2
1800
11th to 20thNight
50%49%22%14%2
1775
21st to endNight
54%6%6%15%16%3
1684
May1st to 10thNight
47%6%8%18%15%5%
1440
11th to 20thNight
43%6%9%23%16%3
1416
21st to endNight
36%8%16%19%19%3
1551
June1st to 10thNight
45%9%13%23%9%1
1440
11th to 20thNight
39%8%12%22%17%2
1440
21st to endNight
43%11%14%19%13%1
1440
July1st to 10thNight
33%10%12%26%17%2
1400
11th to 20thNight
36%7%14%29%13%
1392
21st to endNight
34%9%17%25%14%
1486
August1st to 10thNight
36%11%17%23%13%1
1496
11th to 20thNight
34%9%16%29%11%
1598
21st to endNight
36%8%15%29%11%1
1959
September1st to 10thNight
37%8%13%27%14%1
1800
11th to 20thNight
34%8%14%33%10%1
1800
21st to endNight
41%7%13%30%9%
2047
October1st to 10thNight
46%7%11%21%15%
2160
11th to 20thNight
52%8%12%19%7%
2160
21st to endNight
56%8%14%15%8%
2489
November1st to 10thNight
50%6%15%20%9%
2432
11th to 20thNight
54%8%12%17%8%1
2660
21st to endNight
61%7%12%15%4
2660
December1st to 10thNight
68%7%10%11%3
2660
11th to 20thNight
63%5%10%15%7%1
3288
21st to endNight
73%6%6%12%3
4884

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
22%22%33%19%4
180
11th to 20thDay
30%17%36%11%5%
168
21st to endDay
22%19%38%16%5%
222
February1st to 10thDay
31%28%31%9%2
240
11th to 20thDay
30%25%40%5%1
240
21st to endDay
31%22%33%12%2
322
March1st to 10thDay
27%19%35%16%3
420
11th to 20thDay
25%20%34%16%31
420
21st to endDay
32%20%27%15%5%
462
April1st to 10thDay
30%20%30%13%6%
420
11th to 20thDay
31%21%20%17%9%2
412
21st to endDay
29%19%32%13%6%1
420
May1st to 10thDay
27%15%29%19%8%2
423
11th to 20thDay
20%17%32%21%7%3
447
21st to endDay
20%16%32%20%10%3
485
June1st to 10thDay
25%13%32%20%8%1
450
11th to 20thDay
18%15%30%23%11%3
450
21st to endDay
17%14%33%22%12%2
450
July1st to 10thDay
10%8%29%34%14%4
445
11th to 20thDay
11%9%33%27%16%4
444
21st to endDay
14%9%33%29%12%3
488
August1st to 10thDay
13%6%31%30%14%5%
446
11th to 20thDay
13%7%27%31%16%7%
439
21st to endDay
14%12%28%25%14%7%
495
September1st to 10thDay
14%10%31%22%14%8%
450
11th to 20thDay
13%12%25%24%17%8%
450
21st to endDay
18%14%30%19%14%6%
450
October1st to 10thDay
24%16%24%21%11%4
450
11th to 20thDay
24%22%30%17%5%2
450
21st to endDay
30%21%26%19%41
437
November1st to 10thDay
24%20%29%19%7%1
337
11th to 20thDay
24%23%34%12%42
180
21st to endDay
29%27%31%9%31
180
December1st to 10thDay
29%21%36%12%2
180
11th to 20thDay
33%23%33%8%21
180
21st to endDay
29%24%32%11%41
198
January1st to 10thNight
25%17%37%18%3
760
11th to 20thNight
27%20%28%20%5%
737
21st to endNight
18%15%38%24%41
792
February1st to 10thNight
22%18%37%19%3
720
11th to 20thNight
20%18%40%19%3
703
21st to endNight
24%20%30%22%4
592
March1st to 10thNight
24%18%34%21%3
720
11th to 20thNight
24%19%33%18%6%1
720
21st to endNight
22%16%31%23%8%
792
April1st to 10thNight
27%16%30%23%5%
720
11th to 20thNight
24%20%28%20%8%
711
21st to endNight
26%14%28%23%8%1
604
May1st to 10thNight
23%9%29%26%11%1
360
11th to 20thNight
22%10%33%28%7%1
354
21st to endNight
14%7%37%29%12%1
389
June1st to 10thNight
16%8%33%34%8%
360
11th to 20thNight
15%9%30%33%12%1
360
21st to endNight
18%9%25%34%14%
360
July1st to 10thNight
7%8%28%41%15%1
350
11th to 20thNight
11%5%27%42%15%1
348
21st to endNight
10%5%27%44%13%2
394
August1st to 10thNight
9%7%24%40%19%1
432
11th to 20thNight
11%225%36%22%3
534
21st to endNight
13%8%27%34%17%2
771
September1st to 10thNight
14%7%28%30%18%2
720
11th to 20thNight
17%7%22%31%20%3
720
21st to endNight
18%10%24%25%20%2
720
October1st to 10thNight
23%12%26%24%14%1
720
11th to 20thNight
24%16%31%20%9%1
720
21st to endNight
27%17%28%23%5%
792
November1st to 10thNight
26%14%28%25%7%
740
11th to 20thNight
24%18%33%15%9%1
760
21st to endNight
30%18%26%20%6%
760
December1st to 10thNight
30%18%32%17%3
760
11th to 20thNight
27%19%32%18%41
760
21st to endNight
32%16%31%17%3
836
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